Date: Thu, 14 Dec 2017 20:26:16 -0800
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Another way to make a CM choke ?
<And not a very good one, because it fails to consider the common mode
<circuit of which it is a part.
<73, Jim K9YC
<On 12/14/2017 1:48 PM, David Robbins wrote:
> Ancient reference for aircore
> baluns:http://www.k1ttt.net/technote/airbalun.html
>
## The chart goes from 1 mhz up to 30 mhz, in 1 mhz increments. As noted he
did
NOT depict the exact freq of resonance. But the concept works, with extreme
high Zs
and all resistive, when at exact resonance. Albeit, they are narrow banded
devices, as can
be seen when going just plus or minus 1 mhz ! To tweak these correctly, they
would have to
be shifted in freq, by adding or subtracting turns, which of course adds or
subtracts both uh
and C. It would take some mucking about, but ideally, one could get the
resonance point
either inside a ham band, or just above a ham band. If just above a ham band,
then a small
amount of external C between input and output braids would lower the
resonance... low
enough to fine tune it to the band of interest.
## But for 160-80-40m, it will use one helluva lot of coax, to even get close
to working with a
high Z, so its impractical for the lower bands, and marginal for the upper
bands. Final verification
could easily be done with any clamp on RF ammeter.
Jim VE7RF
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